Leveling up in Electronics Tools
May. 13th, 2009 08:59 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
tcepsaI am primarily writing this for my own edification. If you find it useful as well, so much the better ^_^
I have either been missing or unable to retain a rather important piece of knowledge pertaining to the usage of electrical measurement tools. If you've ever looked at a digial multimeter, for instance, you've probably noticed that around the dial the settings are marked in units like "2 V" "20 V" etc. I could never figure out why they were marked with a leading two; my brain kept trying to go "Okay, it reads .50, but we're on the 20 V measurement so that actually means that the value being measured is 10 Volts."
This is Very Much Not True.
The value is actually .50 V; the only thing to actually look at is the units on the display and the main number being displayed. The 20 is a reminder that 20 is the upper limit for that scale (actually 19.99). This is because the display is a "3.5 digit" display, meaning that it has 3 full LCD digits and the leftmost one can only display a 1 or be off completely. To help compensate, they shift the decimal point around (which is why you should not pay attention to the fact that it says "20"). When the scale is set to 20 V, the decimal point will be in the middle. The leftmost two digits can go up to 19, and the rightmost can go up to 99, giving you a total of 19.99 V, just under the maximum of 20. (Think of it as a mathematical "open" upper bound).
I have either been missing or unable to retain a rather important piece of knowledge pertaining to the usage of electrical measurement tools. If you've ever looked at a digial multimeter, for instance, you've probably noticed that around the dial the settings are marked in units like "2 V" "20 V" etc. I could never figure out why they were marked with a leading two; my brain kept trying to go "Okay, it reads .50, but we're on the 20 V measurement so that actually means that the value being measured is 10 Volts."
This is Very Much Not True.
The value is actually .50 V; the only thing to actually look at is the units on the display and the main number being displayed. The 20 is a reminder that 20 is the upper limit for that scale (actually 19.99). This is because the display is a "3.5 digit" display, meaning that it has 3 full LCD digits and the leftmost one can only display a 1 or be off completely. To help compensate, they shift the decimal point around (which is why you should not pay attention to the fact that it says "20"). When the scale is set to 20 V, the decimal point will be in the middle. The leftmost two digits can go up to 19, and the rightmost can go up to 99, giving you a total of 19.99 V, just under the maximum of 20. (Think of it as a mathematical "open" upper bound).
